High-speed Ethernet systems such as 10 GBASE-T provide a convenient way to transfer data across existing cable infrastructures. FIG. 1 illustrates one end of a typical Ethernet system 100 that includes a linecard or other mounting structure 102 that receives one or more Ethernet cables 104. The cables plug into a connector interface 106 that provides magnetic isolation and electrostatic discharge (ESD) protection for plural Ethernet transceivers 108. A host computer 110 interfaces with the transceiver circuitry through a serial interface 112.
Due to the high speed of data transfer and the marginal quality of the existing infrastructure cabling, high-speed Ethernet systems are often susceptible to various sources of noise, including radio-frequency interference (RFI) noise. The transceiver circuits are also susceptible to cable discharge events (CDE). These events are generally static discharges that occur as an Ethernet cable is plugged into or comes into close proximity with a corresponding connector.
FIG. 2 illustrates one proposal for handling the problems noted above. A connector interface module 202 (corresponding to the interface 106 of FIG. 1) employs a magnetic package that includes plural transformer circuits 204A-204D that each couple to a respective twisted pair differential Ethernet channel. This effectively isolates each transceiver from CDE events. Termination circuitry 206 provides matching termination impedances for each of the channels. One of the differential channels is tapped for sensing a common-mode signal across a termination resistor, and the common-mode signal is fed into a dedicated transformer circuit 208 via a common-mode detection path 210. The transceiver circuits access the detected common-mode signal and derive a value indicating a level of RFI noise associated with the common-mode signal. Filter circuitry compensates for the noise based on the derived value.
While the separate common-mode channel architecture works well for its intended applications, a separate transformer circuit is utilized, thereby increasing the cost associated with the magnetic package. Accordingly, what is needed is a system and associated method that minimizes cost associated with the magnetic package, yet still provides the capability to cancel the RFI.